Two-channel oscillator



April 25, 1950 c. MCK. WHEELER TWO-CHANNEL OSCILLATOR Filed July 20, 1945 I N VEN TOR. CHRSOA/ M576 WHEELER "quency atwhicirit is intended to operate.

TWU- CHANNEL OSGILLATORH l Garson McKeag -Wlieeler; Montclair, N. J., as-- signer; toaiEederal Telcplione and itadio 06mm= -ration,vl\lew YorkguNi Y accorporation' dfazDelat- Ware T AI IPIiGatiOnJiLIyZO, 1945; Serial"N6I"6U6,213

' 3 Claims. (01% 250F365):

1i. 'I'he'=-'present ir-1Venti0n relates? to electrori': discha'rge device circuits andp'articula rly'to electron discharge device oscillator systems.

In highpower oscillatoi'equipment} such-as for example' equipment having ari input of' the: order oi -hundreds ofkilowatts; which are operated at the lower frequencies; s ncha's'fo'r example of the order of '56 kilocyc1es; long leads must be used -because of. the-large dimensions requiredrof the I proli'ficicaus'e of-parasitic oscillations; which oscil latices are usually undesirableb I An objection the-present invention isthe provision- 0f an improvedi'oscniator system-includin "means: for preventing parasitic: oscillations): pariticularly those due to' long leads.

1 It; is" often advantageous to operateathe same oscillator at: a: selected: one: of tWo -WideIy'diiIeF -ent- -frequenciesisuch as for exampie"; a low' frequency-ini the "order of eii ikilocycles' and 2 high frequency: in the order 0f 20 mega'cyclesi- Such =dual rangenoscillators' arefvaluable for numerous purposes." IEoriexample,-.theyare-not:only a'dvan fit'ageous in communication systems b ut are decid- -"'edly valuablefor seasoning electron discharge "devices andc testing theme. Before electron dis- "charge' deviceszrofi highi p'ower' areused for high frequency-operation 'oi 'the *order of meg'acycies, they are pr'eferablwaged or seasoned at' lotver frequencies; suchas fcr example; at 50 to 1605 .kilocyc'les' over .a pericd oitime-untii they operate smoothly; During this-seasoning process; it is important that no par-a'siticsoccur'fibecause these higher frequency parasitics maycausearcing and other reactions-deleterious to the electron discharge device; After the device has been suitably seasziwried;= it-is thentes-t'ed at the high frey 'using the'same-e'quipment for operation at both thelower "and" higher freqnencies, a substantial 's'avingns obtained; Furthermore, itis advantageous to accomplish-this by" a" simpleadjnst" ment without requiring switching or rearrangemerit of theiapparatuss:

Another object of the present invention is the provision of an OSCiHaiJOPWhiGh isadaptedto operated at a selected one of two Widcly'separated frequencies.-

Still-another object oitl'ief present invention =isrlthe provision of an escillatonadaptedfio:onerate at two lUidBliIfifiE-lfiiifitfid ineqnencies in which, during the oourseofoperation at the lower ireqnency; no parasitics ofsaidhigher? frequency Other and further objectsofthepresent in- "order 'oi I megacycles; At the lower: frequency,

the circuit employed functions as'a Hartley'o'scil later 'and include'slumped "constants'r'inr the" form a shunt 'capacitor lf- Thegrid 3 'is connectedzto 'orreside of'tanii circuit Shy-a long'lead' fl through afihlocking condenser' The anode fl isconnected through a long lead l0 and:blocking condenser'? l 'l 'to 'the other s'id 'oi thetank-circuit 5L Leads 8 and lll areparall'l to each OtHer-"and at the higher frequency; form a transmission line: having an effective lengtlf'of approximately one-quarter Wavelength! The transmission'line: consisting of leads B and l0 tunewb'y a slidablecondenser arrangement l'z which acts as' an effective short at 'the higher frequency hut n'otat the lower frequency.- 'The 'positive side l 3 of a source of anode voltage; isconnectedthr'o'ugh a choke coil 'W-to'a point onl'ad I'll which is a voltage-node for the higher freq-uency or as close to said node as practicalf The-:inductance fiis provided with a' ta-p wane-is co'nne'cted' to"groundby alead I 6. The filamentary-cathode 2": is also connected to "ground in the foliowingmannerr The filamentary cathode-2 1s connected by -two leads I I and I 8" to a transformeriarrangement l 92 the* midpoint of 'whose'secondary is"connected to the negative side 2 6- of the anode'--v01tage =supply; and whose primary is connected to asource ofa-heatingcurrent 2 i 5' "'The two' leads l-l and' lfl' 'aresurrounded by a cylindrical conductor' -n Which is intended to "carrythe alternating current voltages. In'order 'to keep' these alternating current voltages out of th'e--power supply; condensers 23 and 24 connect leads I l andl 8 respectively at "the-'end thereof nearest tube l to the cylindrical conductor 22. 'The-cylindrical conductor" 22' is in'" turn surrounded-by another"outer-conductor 2 5 which mat be-*coaxial' o'rirrany bthenshape and' serves with conductor 22 as a transmission line section. A slidable shorting device 26 is provided between the cylindrical conductor 22 and its outer conductor 25 to vary the efiective length thereof, the outer conductor 25 being connected to ground. A small condenser 21 is also connected between the cylindrical conductor 22 and the outer conductor 25 at the end thereof nearest the tube, this small condenser 21 serving as a Vernier adjustment in adjusting the effective length of the transmission line consisting of conductors 22 and 25 respectively. Energy may be extracted from the system hereindescribed by any suitable means, such as for example, a loop 28 coupled to any one of a number of selected points on one of the lines such as, for example, lead "I.

Cylindrical conductor 22 and outer conductor 25 form a transmission line circuit. If slide 26 is adjusted so that the length of this circuit is a quarter wavelength at the higher frequency, energy will be fed back from said circuit through the tube inter-electrode capacities to the transmission line circuit consisting of leads 8 and I0.

Variations of the position of slider 26 from the exact quarter wavelength position, will vary the phase and amplitude of the energy fed back. In one series of positions of slide 26, energy will be fed back through said inter-electrode tube capacities with such phase and amplitude as to produce oscillations at the higher frequency in the transmission line circuit including leads 8 and I 0. In another series of positions of the slide 26, energy will be fed back in such a direction as to prevent oscillation of the transmission line circuit consisting of leads 8 and I0. For the lower frequency operation, the slide 26 is moved to one of the points which prevents oscillation at the higher frequency. The oscillations at said lower frequency will then be governed primarily by the constants of the lumped constant tank circuit 5. The circuit then operates as a Hartley oscillator circuit. It will be noted that the tap I is arranged close to the grid side of the tank circuit. This position is usually found desirable as not very much feed-back is required in order to produce sustained oscillations. The tendency during the course of this low frequency operation for parasitics to occur will be a minimum since the most probable parasitic, that due to the length of leads 8 and In, is prevented by the adjustment of the slide 26 which prevents oscillation at that frequency. When it is desired to operate the system at the higher frequencies, the slide 26 is adjusted to the optimum oscillation point, which as stated hereinbefore, is a little oif a quarter wavelength. The energy then being fed back through the tube l tends to produce oscillation, the frequency of these oscillations being such that condenser 12 is substantially a short and everything to the right of said condenser l2 may be considered as completely out of the circuit. Fine adjustments both for the optimum oscillation point and for the non-oscillation point at the higher frequencies may be made by adjusting the Vernier condenser 21.

While I have described above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of my invention as defined in the accompanying claims.

I claim:

1. An oscillator system comprising an electrondischarge device having an anode, grid, and cathode, a lumped constant circuit tuned to substan- (5 (Copy in Division 51.)

tially a given frequency, leads coupling said lumped constant circuit to said electron-discharge device to feed back energy from said anode to said grid through said lumped constant circuit, said leads forming a distributed constant circuit equal to approximately a quarter wavelength at a higher frequency than said given frequency, means controlling the frequency at which said system oscillates comprising a tunable distributed-constant feed-back circuit having an electrical length of approximately a quarter wavelength at said higher frequency, and at one setting preventing oscillations of said higher frequency, and at another setting causing oscillations at said higher frequency, Said leads at said higher frequency being effectively short-circuited before the lumped constant circuit whereby no oscillations occur at said given frequency at said another setting.

2. An oscillator system comprising an electrondischarge device having an anode, cathode and grid, a lumped constant tank circuit tuned to substantially a given frequency, means coupling opposite points of said tank circuit to the grid and anode, said means including a pair of leads effectively forming a distributed constant circuit, slidable capacitive means coupling said leads together at any one of a number of selective points thereon, said capacitive means having a substantial reactance at said given frequency but operating as an effective short circuit at a relatively higher frequency, said capacitive means being adjusted to control the effective electrical length of said leads so that they are substantially a quarter wavelength at said higher frequency, a line coupling an intermediate point of said tank circuit to the cathode, said line forming a distributed constant circuit of approximately a quarter wavelength at said higher frequency, means for adjusting the effective length of said line to prevent oscillations at said higher frequency by feeding back energy through the inter-electrode capacities of said device with a given phase and amplitude thus enabling the system to oscillate solely at said given frequency, and for said line to another setting to cause feed-back through said inter-electrode capacities with another phase and amplitude to produce oscillations at said higher frequency, the capacitive means then acting as an effective short circiut of said tank circult to prevent oscillation at said given frequency.

3. An oscillator system for operation at a plurality of frequencies comprising an electron-discharge device having grid, plate and cathode electrodes, a lumped circuit tuned to one of said frequencies, a parallel transmission line substantially a quarter wavelength long at another frequency for coupling said lumped circuit between the grid and plate electrodes, a coaxial transmission line having an adjustable electrical length at said other frequency coupled between said cathode electrode and said lumped circuit.

CARSON McKEAG WI-EEELER.

REFERENCES CITED The ioliowing -c. :ences are of record in the file of this patent:

Radio Engineers Handbook, by F. E. Terman; McGraw-I-Iill Co. Inc. (1943), pages 498-502.

Number 

